PROBLEM TO BE SOLVED: To prevent fuel gas consisting of hydrogen contained in the electrode catalyst layer of an anode or oxidant gas consisting of oxygen and air contained in the electrode catalyst layer of a cathode from getting out from the outer periphery of the electrode catalyst layer to the outside of an electrode part, as well as to prevent a membrane part from being creased when a membrane electrode assembly is produced.SOLUTION: A membrane electrode assembly for solid polymer fuel batteries, indicated by numeral 12, comprises: a polymer electrode membrane 1; and a first electrode catalyst layer 2 and a second electrode catalyst layer 3 each composed of catalyst particles, a conductive material adjacent to the catalyst particles and a polymer electrolyte, and holding the polymer electrode membrane 1 therebetween. In at least one part of the edge section 21 of at least one of the first electrode catalyst layer 2 and the second electrode catalyst layer 3, a density of the electrode catalyst layer obtained by summing the catalyst particles, the conductive material adjacent to the catalyst particles and the polymer electrolyte is higher than a density in the rest, except one part, of the electrode catalyst layer obtained by summing the catalyst particles, the conductive material adjacent to the catalyst particles and the polymer electrolyte.
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